JPH11255917A - Polyester film for laminating on metal plate and fabricating the laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film for laminating on a metal plate and fabricating the laminate, having excellent moldability and improved taste and smell holdability, especially improved taste and smell holdability after retorted. SOLUTION: This polyester film comprises a biaxially oriented film produced from a polyethylene terephthalate copolymer having a melting point of 210-245 deg.C, satisfies the following inequalities I and II: Tg>=78 I and Te-Tg<=30 II [Tg is a glass transition temperature ( deg.C) measured with DSC, after thermally melted at 290 deg.C and subsequently quenched; Te is the maximum peak temperature ( deg.C) of the loss modulus of the film], and contains metal terephthalate salt particles or alkylene terephthalate component-containing metal salt particles having an average particle diameter of 0.05-2.5 μm in an amount of 0.005-3 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for laminating and forming a metal plate, and more particularly, it shows excellent formability when laminating to a metal plate and performing can forming such as drawing. The present invention relates to a polyester film for metal plate lamination processing capable of producing metal cans, such as beverage cans and food cans, which are excellent in properties, retort resistance, flavor preserving property, impact resistance and the like.

[0002]

2. Description of the Related Art Metal cans are generally coated to prevent corrosion on the inner and outer surfaces, but recently, for the purpose of simplifying the process, improving hygiene, and preventing pollution, rust prevention is performed without using an organic solvent. Development of a method for obtaining the property has been advanced, and as one of the methods, coating with a thermoplastic film has been attempted.

[0003] That is, a method of laminating a thermoplastic resin film on a metal plate of tin, tin-free steel, aluminum or the like, followed by drawing or the like is being studied.

As the thermoplastic resin film, it is gradually becoming clear that a copolymerized polyester film is suitable in terms of moldability, heat resistance, impact resistance, and taste and fragrance retention. However, this polyester film does not necessarily show sufficient flavor retention and aroma when the beverage contains extremely important tastes such as green tea and mineral water which is required to be tasteless and odorless. Is sensed.

On the other hand, Japanese Patent Application Laid-Open No. Hei 6-116376 proposes a polyester film for forming a metal sheet having an improved flavor, comprising a copolymerized polyester containing a specific amount of an alkali metal element and a germanium element. I have. However, when this film is used, it shows excellent flavor and fragrance retention in the process where heat is not applied at the stage of filling contents such as a cold pack system, but at the stage of filling contents such as retort treatment. In the step in which the heat treatment is performed, sufficient flavor and fragrance retention cannot always be obtained.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art and to maintain the excellent heat resistance, impact resistance, and retort resistance of a copolyester film. An object of the present invention is to provide a polyester film for metal plate laminating processing, which is excellent in moldability, and has improved flavor retention and flavor retention, in particular, retention retention after retort treatment.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, using a copolymerized polyethylene terephthalate having a specific melting point, a specific glass transition temperature and a dynamic viscosity. A film having elasticity and having a specific amount of externally precipitated particles having an average particle diameter within a specific range, while maintaining excellent molding processability, can maintain the flavor and aroma retention, especially the retention of the flavor after retort treatment. The present inventors have found that the fragrance can be remarkably improved, and have reached the present invention.

That is, the present invention has a melting point of 210 to 24.
A biaxially stretched film made of copolymerized polyethylene terephthalate at 5 ° C., wherein the highest temperature peak temperature (Te) of the loss modulus of the film and the glass transition temperature (Tg) in DSC measurement are represented by the following formula (1) and It contains 0.005 to 3% by weight of particles of a metal terephthalate or a metal salt containing an alkylene terephthalate component which satisfies the formula (2) and has an average particle diameter of 0.05 to 2.5 μm. It is a polyester film for metal plate lamination processing.

[0009]

Tg ≧ 78 (1) Te−Tg ≦ 30 (2) (where, Tg is the glass transition temperature (° C.) in DSC measurement after 290 ° C. heating-quenching, and Te is the loss elasticity of the film. Rate is the highest peak temperature (° C).)

Preferably, the copolymerized component of the copolymerized polyethylene terephthalate is 2,6-naphthalenedicarboxylic acid, and the amount of extraction when the film is extracted with ion-exchanged water at 121 ° C. for 2 hours. Is 0.
It is preferably 5 mg / inch ² or less.

In the present invention, among various copolymerized polyesters, while retaining excellent heat resistance, impact resistance and retort resistance, the flavor retention and, in particular, the flavor retention after retort treatment are maintained. Therefore, a copolymerized polyester having ethylene terephthalate as a main repeating unit, that is, a copolymerized polyethylene terephthalate (hereinafter sometimes abbreviated as a copolymerized PET) is used.

The copolymerized PET in the present invention is a substantially linear copolymerized polyester comprising terephthalic acid as a main dicarboxylic acid component and ethylene glycol as a main glycol component.

In the present invention, the copolymerization component of the copolymerized PET may be a dicarboxylic acid component or a diol component.

The dicarboxylic acid component includes aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decane dicarboxylic acid; Alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be exemplified.
Examples thereof include aliphatic diols such as -butanediol, 1,6-hexanediol, and diethylene glycol; alicyclic diols such as 1,4-cyclohexanedimethanol; and aromatic diols such as bisphenol A. These can be used alone or in combination of two or more.

The proportion of the copolymerization component depends on the kind thereof, but the proportion is such that the melting point of the polymer is in the range of 210 to 245 ° C., preferably 215 to 240 ° C. If the melting point is lower than 210 ° C., the heat resistance will be poor. On the other hand, when the melting point exceeds 245 ° C., the crystallinity of the polymer is too large and the moldability is impaired.

Here, the melting point of the copolymerized PET was measured by Du.
Pont Instruments 910 DSC
And determining a melting peak at a heating rate of 20 ° C./min. The sample amount is 20 mg.

Further, the intrinsic viscosity (orthochlorophenol, 35 ° C.) of the copolymerized PET used in the present invention is 0.52.
To 1.50, more preferably 0.57 to 1.00, particularly preferably 0.60 to 0.8.
0. If the intrinsic viscosity is less than 0.52, the impact resistance may be insufficient, which is not preferable. On the other hand, when the intrinsic viscosity exceeds 1.50, the moldability may be impaired.

The copolymerized PET in the present invention is not limited by its production method, but is obtained by subjecting terephthalic acid, ethylene glycol and a copolymerized component to an esterification reaction.
Then, the obtained reaction product is subjected to a polycondensation reaction until a desired degree of polymerization is obtained to give a copolymerized PET, or dimethyl terephthalate, ethylene glycol and a copolymer component are subjected to a transesterification reaction, and then obtained. A preferred example is a method of subjecting the reaction product to a polycondensation reaction until a desired degree of polymerization is obtained to obtain a copolymerized PET. Further, the copolymerized PET obtained by the above method (melt polymerization) can be converted into a polymer having a higher degree of polymerization, if necessary, by a polymerization method in a solid state (solid state polymerization).

If necessary, an antioxidant, a heat stabilizer, a viscosity modifier, a plasticizer, a hue improver,
Additives such as lubricants, nucleating agents, and UV absorbers can be added.

The catalyst used in the polycondensation reaction includes:
Antimony compounds (Sb compounds), titanium compounds (Ti
Compounds) and germanium compounds (Ge compounds), among which titanium compounds and germanium compounds are more preferable from the viewpoint of film taste and fragrance retention. Preferred examples of the titanium compound include titanium tetrabutoxide and titanium acetate. As the germanium compound, (a) amorphous germanium oxide, (b) fine crystalline germanium oxide, and (c) germanium oxide were dissolved in glycol in the presence of an alkali metal or an alkaline earth metal or a compound thereof. A solution, a solution obtained by dissolving germanium oxide in water, and the like are preferable. Further, when used in combination with an antimony compound and / or a titanium compound,
It is preferable because the production cost can be reduced together with the improvement of the taste and fragrance retention.

The polyester film of the present invention is used in a state of being biaxially stretched and heat set. At this time, the highest temperature peak temperature (Te) of the loss modulus of the polyester film
And the glass transition temperature (Tg) in the DSC measurement must satisfy the following expressions (1) and (2).

[0022]

Tg ≧ 78 (1) Te−Tg ≦ 30 (2) (where Tg is the glass transition temperature (° C.) in DSC measurement after heating and melting and quenching at 290 ° C., and Te is the loss elasticity of the film. Rate is the highest peak temperature (° C).)

If the Tg of the film is less than 78 ° C., the heat resistance becomes poor, and the flavor and odor retention after retorting deteriorates. For this reason, as the copolymerization component of the copolymerized PET, it is preferable to use, as at least one component, a component whose glass transition temperature does not change or increases when the proportion of the copolymerization component is increased. Preferred examples of the component that increases the glass transition temperature when the proportion of the copolymer component is increased are 2,6-naphthalenedicarboxylic acid as the dicarboxylic acid component, and 1,4-cyclohexanedimethanol as the diol component. it can.

Here, the Tg of the polyester was measured by placing a 20 mg film sample in a pan for DSC measurement,
After heating and melting for 5 minutes on a heating stage, the sample pan was quickly cooled and solidified on an aluminum foil spread on ice,
A method of determining a glass transition point at a heating rate of 20 ° C./min using on Instruments 910 DSC.

Further, when the value of Te-Tg exceeds 30, the molecular orientation and the crystallinity of the film become too high, so that the moldability is remarkably reduced. Although the value of Te depends on the copolymerization component and the copolymerization amount, a method of adjusting the film forming conditions, particularly the biaxial stretching ratio, the stretching temperature, and the heat setting temperature, is preferably mentioned.

Here, Te is determined at a measurement frequency of 10 Hz and a dynamic displacement of ± 25 × 10 ⁻⁴ cm using a dynamic viscoelasticity measuring device.

In the present invention, the average particle size of the copolymerized PET is 0.05 to 2.5 μm, preferably 0.1 to 2.2.
Particles of metal terephthalate or metal salt containing an alkylene terephthalate component having a size of 5 μm, more preferably 0.3 to 2 μm, are contained as a lubricant. If the average particle size is less than 0.05 μm, the effect of improving the slipperiness is insufficient, and the winding property in the film manufacturing process is unfavorably deteriorated. On the other hand, when the average particle size exceeds 2.5 μm, coarse particles (for example, particles of 10 μm or more) become a starting point in a portion deformed by processing of a deep drawing can or the like, and pinholes or breaks occur in some cases. It is not preferable. Specific examples of such metal salt particles include:

[0028]

Embedded image

And the like. Preferable examples of the metal forming the metal salt particles include an alkali metal and an alkaline earth metal.

The metal salt particles are not limited by the production method. As a representative example, a production example of calcium terephthalate particles will be described.An aqueous solution of terephthalic acid is added to an aqueous solution of calcium chloride to precipitate calcium terephthalate, the calcium terephthalate is separated, washed with water, dried, and then anhydrous terephthalic acid. Calcium is dispersed in a glycol such as ethylene glycol to form a slurry, and the slurry is subjected to a conventional particle size adjustment treatment, for example, a pulverization treatment, a classification treatment, etc., to obtain a glycol slurry in which calcium terephthalate having a predetermined average particle diameter is dispersed. be able to. The ethylene terephthalate component or the metal salt particles containing the ethylene terephthalate component and the phosphorus component can be produced by a known method for preparing internally precipitated particles.
It must be performed in a system different from the system for producing T.

The content of precipitated particles in the copolymerized PET is as follows:
It must be 0.005 to 3% by weight, preferably 0.01 to 1% by weight, more preferably 0.05 to 0.
5% by weight. If the amount is less than 0.005% by weight, the effect of improving the slipperiness is insufficient. On the other hand, if it exceeds 3% by weight, the film frequently breaks, which is not preferable. If necessary, other lubricants can be added as long as the effects of the present invention are not impaired.

As a means for incorporating a lubricant into the polyester, conventionally known means can be used and is not particularly limited, but a method in which a lubricant is added during the production of the copolymerized polyester is preferable.

The surface roughness (Ra) of the film of the present invention is:
15 nm or less in terms of film windability and flavor and fragrance retention,
In particular, the thickness is preferably 4 to 15 nm.

The surface roughness (Ra) of the film is J
This is the center line average roughness determined according to IS-B0601, and a portion of the measured length L is extracted from the film surface roughness curve in the direction of the center line, the center line of the extracted portion is defined as the X axis, and the longitudinal magnification Is the Y axis, the roughness curve Y = f
When represented by (x), the value (Ra;
nm) is defined as the film surface roughness.

[0035]

(Equation 4)

In the present invention, Ra is expressed as an average value of four pieces of five pieces measured with a reference length of 2.5 mm, excluding one piece from the larger value.

Since the polyester film of the present invention is used particularly for food cans or beverage cans, it is better that the amount of substances eluted or scattered from the film is smaller, but it is substantially impossible to eliminate such substances at all. It is possible. Therefore, for use in food cans or beverage cans, for example, the extraction amount per square inch of a film when extracted with ion-exchanged water at 121 ° C. for 2 hours is 0.5 mg.
Or less, more preferably 0.1 mg or less.

In order to reduce the amount of extraction, the glass transition temperature of the film may be increased. The glass transition temperature of the film is determined by the glass transition temperature and the degree of orientation of the polymer constituting the film. However, if the degree of orientation is increased, the moldability deteriorates. Therefore, it is necessary to increase the glass transition temperature of the polymer (copolymerized PET). Is preferred.

The refractive index in the thickness direction of the film is 1.
500 to 1.540, preferably 1.505
More preferably, it is 1.530. If the refractive index is too low, the moldability will be insufficient, while if it is too high, the structure will be close to amorphous, and the heat resistance may decrease.

Here, the refractive index in the thickness direction of the film is
A polarizing plate analyzer is attached to the eyepiece side of the Abbe refractometer, and the measurement is performed using a monochromatic NaD line. The mounting solution uses methylene iodide, and the measurement temperature is 25 ° C.

The film of the present invention preferably has a thickness of 6
７５75 μm. 8 to 75 μm, especially 10 to 50
μm is preferred. If the thickness is less than 6 μm, breakage or the like tends to occur during processing, while if it exceeds 75 μm, the quality is excessive and uneconomical.

A metal plate on which the film of the present invention is bonded,
In particular, as a metal plate for can making, a plate of tin, tin-free steel, aluminum or the like is suitable. The bonding of the polyester film to the metal plate can be performed, for example, by the following method. The metal plate is heated to a temperature equal to or higher than the melting point of the film, the film is laminated, and then cooled. The surface layer (thin layer) of the film in contact with the metal plate is made amorphous and adhered. An adhesive layer is primer-coated on the film in advance, and this surface is bonded to a metal plate. As the adhesive layer, a known resin adhesive, for example, an epoxy adhesive, an epoxy-ester adhesive, an alkyd adhesive, or the like can be used.

[0043]

The present invention will be further described with reference to the following examples.
The properties of the film were measured by the following methods. (1) Intrinsic viscosity of polyester Measured in orthochlorophenol at 35 ° C.

(2) Melting point of polyester Du Pont Instruments 910 D
A method in which a melting peak is determined at a heating rate of 20 ° C./min using SC. The sample amount is 20 mg.

(3) Glass transition temperature of polyester (T
g) 20 mg of a film sample was placed in a pan for DSC measurement, heated and melted for 5 minutes on a 290 ° C. heating stage, and then rapidly cooled and solidified on an aluminum foil spread on ice, and then Du Pont Instruments 910 was prepared.
A method in which the glass transition point is determined at a heating rate of 20 ° C./min using DSC.

(4) Maximum peak temperature of loss elastic modulus of film (Te) The loss elastic modulus was determined at a measurement frequency of 10 Hz and a dynamic displacement of ± 25 × 10 ⁻⁴ cm using a dynamic viscoelasticity measuring apparatus. The peak temperature at this time is shown.

(5) Average Particle Size Particles The internally deposited particles are separated from the film sample by a known method, and the individual particles are scattered so as not to overlap with each other as much as possible.
It is formed at a size of ~ 30 nm, observed with an operation-type electron microscope at a magnification of 10,000 to 30,000, image-processed by Luzex 500 manufactured by Nippon Regulator Co., Ltd., and the average particle size is determined from 100 particles.

(6) Winding property In the film manufacturing process, when the film was wound into a roll, small protrusions on the roll surface caused by poor slippage were observed and evaluated according to the following criteria. ◎: No small protrusion was observed at all. ：: Some small protrusions are observed, but there is no particular problem in handling. X: Many small protrusions are generated, and the handleability deteriorates.

(7) Deep drawing workability The film was heated to a temperature equal to or higher than the melting point of polyester.
Affixed to both sides of 25 mm tin-free steel, water-cooled, cut into a 150 mm diameter disk, deep-drawn in four stages using a drawing die and punch, and a 55 mm diameter side-side seamless container (hereinafter referred to as can and Abbreviated). The following observations and tests were performed on the cans, and the cans were evaluated according to the following criteria. Deep drawing processability-1 ○: No whitening or breakage is observed in the film processed without any abnormality. Δ: Whitening was observed on the upper part of the film can. X: Film breakage is observed in a part of the film. Deep drawing processability-2 ○: Processed without abnormality, rust prevention test of film surface in can (1% NaCl aqueous solution was put in the can, electrodes were inserted, and a voltage of 6 V was applied using the can body as an anode. The current value at that time is measured, and is 0.2 mA or less in the ERV test. ×: There is no abnormality in the film, but the current value exceeds 0.2 mA in the ERV test, and pinhole-shaped cracks starting from the coarse lubricant of the film are observed when the energized portion is observed under magnification.

(8) Impact resistance For cans with good deep drawing, pour water thoroughly, cool to 0 ° C., drop 10 pieces for each test from a height of 30 cm onto a PVC tile floor. As a result of the ERV test in the can, the results were as follows: ○: 0.2 mA or less for all 10 samples. Δ: Exceeded 0.2 mA for 1 to 5 pieces. X: More than 6 pieces exceeded 0.2 mA, or cracking of the film was already observed after dropping.

(9) Heat Embrittlement Resistance The can which had good deep drawing was heated and held at 200 ° C. for 5 minutes, and the above-mentioned impact resistance was evaluated. ○: 0.2 mA or less for all 10 pieces Met. Δ: Exceeded 0.2 mA for 1 to 5 pieces. ×: Exceeding 0.2 mA for 6 or more pieces, or cracking of the film was already observed after heating at 200 ° C. × 5 minutes.

(10) Retort resistance The cans having good deep drawing properties are filled with water and retorted in a steam sterilizer at 120 ° C. for 1 hour.
Stored at 50 ° C. for 30 days. After dropping 10 cans for each test from a height of 50 cm onto a PVC tile floor, an ERV test in the cans was performed. ：: 0.2 mA or less for all 10 samples. Δ: Exceeded 0.2 mA for 1 to 5 pieces. X: More than 6 pieces exceeded 0.2 mA, or cracking of the film was already observed after dropping.

(11) Flavor Retention and Flavor-1 For cans with good deep drawing, filled with ion-exchanged water and stored at room temperature (20 ° C.) for 30 days. Using the immersion liquid, a tasting test was conducted by 30 panelists, compared with ion-exchanged water for comparison, and evaluated according to the following criteria. ：: Three or less out of thirty felt changes in taste and aroma as compared with the comparative solution. 〇: Four to six out of thirty people felt a change in taste and aroma as compared with the comparative solution. Δ: 7 to 9 out of 30 persons felt a change in taste and aroma as compared with the comparative solution. ×: Ten or more of the 30 persons felt a change in taste and aroma as compared with the comparative solution.

(12) Flavor preservation and flavor retention-2 The cans having good deep drawability were filled with ion-exchanged water, subjected to a retort treatment in a steam sterilizer at 120 ° C. for 1 hour, and then at room temperature (20 ° C.). C) Store for 30 days. Using the immersion liquid, a tasting test was conducted by 30 panelists, compared with ion-exchanged water for comparison, and evaluated according to the following criteria. ：: Three or less out of thirty felt changes in taste and aroma as compared with the comparative solution. 〇: Four to six out of thirty people felt a change in taste and aroma as compared with the comparative solution. Δ: 7 to 9 out of 30 persons felt a change in taste and aroma as compared with the comparative solution. ×: Ten or more of the 30 persons felt a change in taste and aroma as compared with the comparative solution.

[Examples 1 to 5 and Comparative Examples 1 and 2]
After drying the copolymerized PET (intrinsic viscosity 0.64, containing 0.3% by weight of calcium terephthalate having an average particle diameter of 0.8 μm) obtained by copolymerizing the copolymerized components shown in (1), melt-extruded and quenched and solidified. A stretched film was obtained. Next, after stretching this unstretched film longitudinally at the temperature and magnification shown in Table 1,
The film was transversely stretched at the temperature and magnification shown in Table 1 and further heat-set at 180 ° C. to obtain a biaxially stretched film.

The thickness of the obtained film was 25 μm, and the surface roughness (Ra) was 14 nm. Table 2 shows the glass transition temperature (Tg) and the maximum peak temperature (Te) of the loss modulus, the refractive index in the thickness direction of the film, and the extraction amount of ion-exchanged water, and Table 3 shows the evaluation results.

[0057]

[Table 1]

[0058]

[Table 2]

[0059]

[Table 3]

As is clear from the evaluation results in Table 3, in the case of the present invention in which the melting point of the copolymerized PET is 210 to 245 ° C. (Examples 1 to 5), good results were obtained. When the temperature was lower than 210 ° C. (Comparative Example 1), the heat resistance was inferior, and the taste and flavor retention after retort treatment was poor. When the temperature exceeded 245 ° C. (Comparative Example 2), the moldability was poor.

[Examples 6 and 7 and Comparative Examples 3 and 4] In Example 5, the unstretched copolymers obtained by melt-extruding and quenching and solidifying the copolymerized PETs having different copolymerization ratios as shown in Table 4 were obtained. The films were stretched and heat-set under the conditions shown in Table 4 to obtain biaxially stretched films.

The thickness of the obtained film was 25 μm, the surface roughness (Ra) and the glass transition temperature (T
g), the maximum peak temperature (Te) of the loss elastic modulus, the refractive index in the film thickness direction, and the extraction amount of ion-exchanged water are shown in Table 5.
Table 6 shows the evaluation results.

As is clear from the evaluation results in Table 6, Tg
In the case of the present invention where is not less than 78 ° C. and Te-Tg is not more than 30 ° C. (Examples 6 and 7), good results were obtained.
When g is less than 78 ° C. (Comparative Example 3), heat resistance is poor,
When the taste and aroma retention after retort were poor and Te-Tg exceeded 30 ° C. (Comparative Example 4), the moldability deteriorated.

[0064]

[Table 4]

[0065]

[Table 5]

[0066]

[Table 6]

[Examples 8 to 15 and Comparative Examples 5 to 8] In Example 2, biaxially stretched films were obtained in which the average particle size and content of calcium terephthalate were changed as shown in Table 7. Table 7 shows the surface roughness (Ra) of the obtained film, and Table 8 shows the evaluation results.

The average particle size of the calcium terephthalate particles is 0.05 to 2.5 μm and the content is 0.005 to 3.
In the case of the present invention, which is 0% by weight (Examples 8 to 15), good results were obtained, but when the average particle size was less than 0.05 μm (Comparative Example 5) and the content was 0.005% by weight. % (Comparative Example 7), the effect of improving the slipperiness is insufficient.
When the winding property of the film is deteriorated and the average particle size exceeds 2.5 μm (Comparative Example 6) and when the content exceeds 3.0% by weight (Comparative Example 7), pinholes or the like during deep drawing are formed. It was easily broken and was unsuitable.

[0069]

[Table 7]

[0070]

[Table 8]

[Embodiments 16 to 18] In the embodiment 2,
Instead of calcium terephthalate, the following compound (1) was used in Example 16 and the following compound (2) was used in Example 17.
In Example 18, the following compound (3) was added, and the other conditions were the same as in Example 2 to obtain a biaxially stretched film. The average particle size and content of each additive compound were the same as in Example 2.

[0072]

Embedded image

The thickness of the obtained film was as shown in Examples 16 to 1.
8 were 25 μm each, and the surface roughness (Ra) of the film was 13 nm in Example 16 and 1 in Example 17.
5 nm and 13 nm in Example 18. The evaluation results are as shown in Table 9, and good results were obtained as in Example 2.

[Comparative Example 9] In Example 2, instead of calcium terephthalate, silica particles having an average particle diameter of 0.8 µm were dispersed in ethylene glycol, and added so that the content became 0.3% by weight. The other conditions were the same as in Example 2 to obtain a biaxially stretched film.

The thickness of the obtained film was 25 μm, and the surface roughness (Ra) of the film was 16 nm.
The evaluation results are as shown in Table 9, and the characteristics were slightly inferior to those of Example 2.

[0076]

[Table 9]

[0077]

The polyester film for laminating and forming a metal plate of the present invention has a copolyester in forming a metal can by laminating with a metal plate and then forming the metal can, for example, by deep drawing. While maintaining excellent heat resistance, impact resistance, and retort resistance, it has excellent moldability, and has improved flavor retention and fragrance retention, especially after retort. Is extremely useful.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08K 5/12 C08K 5/12 C08L 67/02 C08L 67/02 // B29K 67:00 B29L 7:00

Claims (3)

[Claims] 1. A biaxially stretched film made of a copolymerized polyethylene terephthalate having a melting point of 210 to 245 ° C., wherein a maximum temperature peak temperature (T
e) and a metal terephthalate or alkylene terephthalate having a glass transition temperature (Tg) in DSC measurement satisfying the following formulas (1) and (2) and having an average particle size of 0.05 to 2.5 μm: A polyester film for laminating a metal plate, comprising 0.005 to 3% by weight of particles of a metal salt containing a component. Tg ≧ 78 (1) Te−Tg ≦ 30 (2) (where Tg is the glass transition temperature (° C.) in DSC measurement after heating and melting and quenching at 290 ° C., and Te is the loss elasticity of the film. Rate is the highest peak temperature (° C).) 2. The polyester film according to claim 1, wherein the copolymerized component of the copolymerized polyethylene terephthalate is 2,6-naphthalenedicarboxylic acid. 3. The film is treated with ion-exchanged water at 121.degree.
The amount of extraction when the time extraction process is performed is 0.5 mg / inch
^The polyester film for laminating and processing a metal plate according to claim 1 or 2, which is ² or less.